6 files declare their use of LanguageManager in Zircon Profile 8

ConfigurableLanguage.php in core/modules/language/src/Entity/ConfigurableLanguage.php

Contains \Drupal\language\Entity\ConfigurableLanguage.

ConfigurableLanguageManager.php in core/modules/language/src/ConfigurableLanguageManager.php

Contains \Drupal\language\ConfigurableLanguageManager.

install.core.inc in core/includes/install.core.inc

API functions for installing Drupal.

InstallerLanguagePageTest.php in core/modules/system/src/Tests/Installer/InstallerLanguagePageTest.php

Contains \Drupal\system\Tests\Installer\InstallerLanguagePageTest.

LanguageAddForm.php in core/modules/language/src/Form/LanguageAddForm.php

Contains \Drupal\language\Form\LanguageAddForm.

SelectLanguageForm.php in core/lib/Drupal/Core/Installer/Form/SelectLanguageForm.php

Contains \Drupal\Core\Installer\Form\SelectLanguageForm.